Disc brakes pros and cons

stueys

Don’t think we’ve done this debate yet.....;-)

The bike industry is only going one way, so if you want to future proof then discs are the obvious choice. Manuafacturers are already stopping running two versions of frames and are designing ground up for discs.

There are numerous advantage to discs - all round consistently better braking peformance, no issue of heat build up on carbon clinchers, allows wheels to be fully aero shaped to the tyre lip, allows wider tyre clearance, etc, etc. The only downside is a slight increase in overall weight.

I run discs on my winter/gravel bike and rim brakes on my nice bike. When I change the nice bike it will be to discs, I’m not in a huge rush to do that because of my investment in wheels.

mercia_man

Here’s an interesting article by cycling science guru Jan Heine who suggests discs are great for mountain bikes but not really of benefit for narrow tyre road bikes.

https://janheine.wordpress.com/2018/07/ ... im-brakes/

keef66

BikerGroveish wrote:

The biggest pro is that they reduce rim wear. The cons of using them on a road bike are so numerous it makes it a bad idea.

Not wanting a pointless argument, but for the record I disagree on both points. If I do treat myself to a new road bike when I retire it will have hydraulic discs, thru axles, clearance for wider tyres and proper mudguards, and internal cables. It might even be a steel framed Mason Resolution...

bobones

One major disadvantage for me is noise. I seriously considered disc brakes for winter bike use, but the number of times I've been out in groups with squealing or grinding discs disturbing the peace really put me off. I know this can be partly due to poor setup, but pad contamination during a ride can also cause issues.

Another is there seems to exist a binary failure mode: one minute you're fine, the next there is no stopping power whatsoever. I have witnessed this for myself and it was enough for the rider involved to sell his disc equipped winter bike and go back to rim brakes.

Weight is definitely a disadvantage if you are at all concerned with the overall mass of your bike, even if just for vanity, not practical, reasons. My good bike is 6.9kg with rim brakes, which would be unattainable with discs at any reasonable cost.

In the west of Scotland, we get a lot of rain, so I ride a lot in the wet. I have yet to experience any dangerous situations with my rim brake equipped bikes in the rain. I've recently built up a new wet weather/winter bike with Shimano R7000 calipers and the stopping power is very impressive, and more than adequate for me in any weather conditions.

The major advantage of discs for me was prolonging wheel life, I have burned through rims very quickly riding in winter, but I can now build my own wheels and re-rim them very economically so this is now much less of a selling point, but still remains the most obvious advantage to my eyes.

In short I am sticking with rim brakes for the foreseeable future. Despite current trends, I don't need tyres wider than 25mm on any of my bikes and the performance of current caliper brakes is excellent in my experience.

CitizenLee

Shirley Basso wrote:

CitizenLee wrote:

flight147z wrote:

CitizenLee wrote:

flight147z wrote:

To me the major disadvantage of disc brakes is that unless you have deep rims (>50mm) they look terrible

For some reason they look ok on aero bikes, but I think they spoil the look of a lot of bikes they are fitted to

That's not really a disadvantage, just a subjective opinion.

Do you think disc brakes look good on road bikes?

In all honesty bicycle brake aesthetics have never been a major concern for me.

Lifetime ban

Believe me I'm guilty of far worse... but yeah, bring on the ban

slowbike

The trend is for wider and wider tyres - I can see why - our road surfaces are generally poor and 28mm tyres do give a bit more cushioning.

I don't follow trends (never have) - all my drop bar bikes are rim brakes - after the first bike it was a conscious decision as it meant I could swap wheels between bikes - it was fine at the time, but over the winter on my CX bike (full guards & rack for commuting) along the country lanes I could really hear the rim brakes rubbing away those rims, plus once in the cold (snow & ice on the road) and wet (it was snowing) the rim brakes were spectacularly ineffective - and so a hydro disc brake bike for winter would've been preferable.
The only other time I want disc brakes on my road bikes is when I've got a long descent that I need to control the speed of - they don't come along often enough to warrant a change of bikes though.
If I was looking at more cycle touring or just longer hillier rides then I'd probably go for hydro discs.

As for asthetics - first they were just ugly - but some are starting to come in looking "normal" - IMHO (bearing in mind I don't do trends or fashion) the Canyon offerings look nice(r)

pamplemoose

I have a bike with Ultegra rim brakes and a bike with Ultegra discs. I vastly prefer the disc brake bike both in terms of brake feel and aesthetics (although my disc bike is an Oltre XR3 so that might be swinging it). In the wet they can sometimes make a noise like a goose being molested, but a good hard braking motion to clear the surface water on the disc sorts it right out. Braking with discs just feels 'better' and thru-axles are nice to have.

On the other hand discs have a weight penalty and aren't as easy to maintain, although bleeding the latest gen of Shimano brakes is pretty easy.

I still wouldn't want to go back to using rim brakes if I was buying a new bike today though. Axle standards have largely been decided on and the weight penalty will get less over time, especially once more disc specific wheels are produced.

BikerGroveish

You have to bear in mind that the limiting factor of braking is friction between the tyre and the road surface. In the conditions that are often vaunted as where disc brakes are a better bet than rim brakes actually there isn’t enough tyre / road friction to enable the disc brakes to work to their theoretical maximum potential. The rim brake and the disc brake both reach their limits way before the differences occur. It’s a placebo effect of disc brakes that manufacturers exploit, and spin / market to the masses. With a typical MTB / CX environment, the surfaces are usually looser anyway, so the friction limit argument is void and the advantage is purely due to the increased pad to braking surface with wet / cold braking surfaces friction effect.

lettingthedaysgoby

flight147z wrote:

Do you think disc brakes look good on road bikes?

I do, particularly when combined with completely internal/hidden cabling. Way better than an ugly calliper getting in the way of the bikes lines at the front.

meanredspider

BikerGroveish wrote:

You have to bear in mind that the limiting factor of braking is friction between the tyre and the road surface.

That is a fallacy. The vast majority of braking load at the limit is on the front tyre due to weight transfer. At the limit, you’re more likely to go over the bars than lock the front tyre. The rear tyre can’t sustain any braking load due to this weight transfer. There are two things you need to be able to do:
- brake progressively to build load on the front tyre
- modulate the braking load on the front wheel

In my experience, disc brakes are both more predictable and easier to modulate. YMMV

shirley_basso

Disc brakes make logical sense except for aesthetics and replacing wheelsets if you have lots.

kajjal

meanredspider wrote:

BikerGroveish wrote:

You have to bear in mind that the limiting factor of braking is friction between the tyre and the road surface.

That is a fallacy. The vast majority of braking load at the limit is on the front tyre due to weight transfer. At the limit, you’re more likely to go over the bars than lock the front tyre. The rear tyre can’t sustain any braking load due to this weight transfer. There are two things you need to be able to do:
- brake progressively to build load on the front tyre
- modulate the braking load on the front wheel

In my experience, disc brakes are both more predictable and easier to modulate. YMMV

That's what I found the increased braking power at the rotor and having hydraulics rather than stretching cables means more control over the increased power and less effort at the lever. Due to this I can stop my disc braked road bike faster in the dry or wet, even if it decides it is going sideways.

jimmocrates

Have a bike with ultegra rim brakes and a bike with ultegra disc.
+ve:
-Wider tyre clearance for better ride feel
-More reliable braking.I live in lancashire,not the alps,but plenty of the descents round here are ridiculously steep,fast and twisty.Im much more confident descending with discs.
-Less prone to road crud.This is farming country.its not the rain on rim brakes that affects performace,its all the animal excrement and farming debris that gets stuck in and around the rim brakes.

-ve:
-looks.on a sunny day when your bike cats a nice shadow.you are reminded that they are a bit ugly.
-noise. Somebody said they can make a noise like a goose being molested.couldnt put it better.

Glad my last bike was disc and would buy the same again.

green_mark

Kajjal wrote:

meanredspider wrote:

BikerGroveish wrote:

You have to bear in mind that the limiting factor of braking is friction between the tyre and the road surface.

That is a fallacy. The vast majority of braking load at the limit is on the front tyre due to weight transfer. At the limit, you’re more likely to go over the bars than lock the front tyre. The rear tyre can’t sustain any braking load due to this weight transfer. There are two things you need to be able to do:
- brake progressively to build load on the front tyre
- modulate the braking load on the front wheel

In my experience, disc brakes are both more predictable and easier to modulate. YMMV

That's what I found the increased braking power at the rotor and having hydraulics rather than stretching cables means more control over the increased power and less effort at the lever. Due to this I can stop my disc braked road bike faster in the dry or wet, even if it decides it is going sideways.

To add - if the only limiting factor was friction between tyre and road surface, the fact that you can run wider tyres at lower pressures with discs means that you have higher friction.

sloppyschleckonds

Yeah, why cant you buy a rim brake bike that takes wider tyres

dodgy

I'm a big fan of discs, and have never had a bad thing to say about them, until...

I was recently in the French Alps on my Giant Propel Advanced (discs). I'm a confident descender, usually, but the build up of heat when braking made the brakes howl like crazy until eventually it got so bad that I had to pull over to allow them to cool (no. I wasn't dragging, just heaving on them 100m before a hairpin).
Even worse, on getting home I realised the pads are worn already on the front, that's a total of 1800miles on a set of pads. Quite extreme imo. Of course I'll get more miles out of them in my usual North Wales rides, but now I have to make sure I either take spares with me on holiday or put brand new ones immediately prior to going out.
I bought this bike for less faff, not more. My other bike it replaced, a Rose Carbon with rim brakes is still on the original pads at >11000 miles and it's been out to the alps 5 times.

timothyw

Giant spec 140mm rotors front and back don't they? I can't help but feel that's a little underspecced for most of us (well, the larger of us...) with the energy that needs to be dissipated coming down an alpine descent.

I suppose this is one more area where discs rule in the wet, as steam coming off the rotors looks cool.

Discs do undeniably chew through the pads quicker than rim brakes, a problem somewhat compounded by enthusiastic pricing by some manufacturers for their pads. Certainly something to keep an eye on (or have a spare set in your saddle bag).

dodgy

I think they are 140mm, but the rotors aren't ice-tech. Maybe that will give a marginal improvement if I upgrade.

BikerGroveish

green_mark wrote:

BikerGroveish wrote:

You have to bear in mind that the limiting factor of braking is friction between the tyre and the road surface.

Kajjal wrote:

That is a fallacy.

No, that’s physics

green_mark wrote:

To add - if the only limiting factor was friction between tyre and road surface, the fact that you can run wider tyres at lower pressures with discs means that you have higher friction.

Not “only limiting factor” The ultimate limiting factor.

If the traction isn’t there. The bike will ‘toboggan’ with locked up wheels which won’t be bringing anything to the braking party. With suitably low traction conditions there won’t be anything to differentiate between a disc brake at its limit or a rim brake at its limit.

meanredspider

BikerGroveish wrote:

Not “only limiting factor” The ultimate limiting factor.

If the traction isn’t there. The bike will ‘toboggan’ with locked up wheels which won’t be bringing anything to the braking party. With suitably low traction conditions there won’t be anything to differentiate between a disc brake at its limit or a rim brake at its limit.

On ice, diesel or cow sh!t, sure - on most situations that you’ll encounter on a road bike, the weight transfer onto the front tyre will provide the force needed. You need to brake progressively and, in the wet, where it makes the most difference, that’s easier to do on a disc brake because a rim brake needs to clear the water off first.

The ultimate limiting factor tends to be you going over the bars as your centre of mass is much higher than the centre of rotation.

BikerGroveish

meanredspider wrote:

BikerGroveish wrote:

Not “only limiting factor” The ultimate limiting factor.

If the traction isn’t there. The bike will ‘toboggan’ with locked up wheels which won’t be bringing anything to the braking party. With suitably low traction conditions there won’t be anything to differentiate between a disc brake at its limit or a rim brake at its limit.

On ice, diesel or cow sh!t, sure - on most situations that you’ll encounter on a road bike, the weight transfer onto the front tyre will provide the force needed. You need to brake progressively and, in the wet, where it makes the most difference, that’s easier to do on a disc brake because a rim brake needs to clear the water off first.

The ultimate limiting factor tends to be you going over the bars as your centre of mass is much higher than the centre of rotation.

True. If you get pinged over the bars all bets are off

sir_les

Last October I bought a Kinesis Aithein Disc as my year round Road bike and it's specced with Ultegra R8000 mechanical levers and groupset and the older 160mm rotors.
I mainly bought the bike because:
I could ride it all year round and not wear the Carbon wheels out.
It had a threaded BB and I got fed up with press fit BB.
It was on paper cheaper and less fancy than an equivalent carbon bike.
I enjoyed turning up to group rides on a bike most people hadn't heard of, instead of being the "S Works" guy.
It gave me assurance in the wet and descending with the discs.

My negative feedback on my setup:
I love small levers as I like to rest my hands on top of them (favourites are SRAM). The Ultegra mechanical hydraulic levers are big chunky units. I have not really found a comfortable way to rest on them still after nearly a year of use. This is a big negative for me and I can't wait for the technology to catch up. If you look at the Ultegra hydraulic Di2 levers they are very good and I should have maybe considered this setup even for the extra money.

In the Winter months I wore through a set of front pads in 1800 miles.

The brakes can squeal a lot, even in the dry sometimes and this becomes tiresome.

Just my thoughts after my first year of ownership.

sloppyschleckonds

So in summary the Pro's for Disc brakes by owners:
Squeal alot
Changing pads a faf and wear quicker
Levers uncomfortable
1kg weight penalty
Dont stop any better in the wet or dry

Tiesetrotter

I've had my first disc brake bike for about 18 months. Can't see the real big deal.

+ Better in really shite weather
+ No rim replacement
+ Modulation is very good
- Discs squeal on and off regularly
- Disc rub seems to come and go annoyingly regularly
- Expensive to maintain i.e. pads are not cheap
- Old Ultegra 6800 disc hoods are a design abomination

I have now tested the 6870, the hoods are so much better. The shop said to me the latest ice discs are the best so probably less disc rub problems. I'll probably stick with discs, but my lovely summer bike is rim and I look forward to using it. No more squealing and no more using the absolutely crap 6800 hoods. Not a good experience so far for me.

norvernrob

Love them on my commuting bike as the bike gets wet, dirty etc on a regular basis. Extra power or whatever isn’t one of the reasons.

I’ve just spent a week in Annecy and was in the top 3% of the descent of the Forclaz, my Foil with rim brakes was superb, even when braking from 45mph coming up to hairpins. So now I’ve done alpine descents (including other really crap ones with broken surfaces and loose gravel where I had to brake pretty much constantly) I still don’t feel any need whatsoever to buy a frame with discs on my best bike.

I was still a minute slower than Bardet on that descent though...

kajjal

Tiesetrotter wrote:

I've had my first disc brake bike for about 18 months. Can't see the real big deal.

+ Better in really shite weather
+ No rim replacement
+ Modulation is very good
- Discs squeal on and off regularly
- Disc rub seems to come and go annoyingly regularly
- Expensive to maintain i.e. pads are not cheap
- Old Ultegra 6800 disc hoods are a design abomination

I have now tested the 6870, the hoods are so much better. The shop said to me the latest ice discs are the best so probably less disc rub problems. I'll probably stick with discs, but my lovely summer bike is rim and I look forward to using it. No more squealing and no more using the absolutely crap 6800 hoods. Not a good experience so far for me.

Properly setup discs don't rub and only squeal if contaminated unless you are in very heavy rain.

You are not wrong about the cost of replacement pads.

stueys

Always chuckle at everyone arguing why they don’t need better braking performance. I’ve yet to brake from 40+ mph thinking I needed a bit less braking capability....

neeb

It's simple - how much do you brake (on a given bike), and in what conditions? All year-round commuter, no contest, get discs. Road bike to be used for training/leisure/competition in mostly dry, mostly non-urban situations: discs are way OTT and carry lots of individually relatively insignificant disadvantages that nonetheless all add up to outweight the advantages.

svetty

NorvernRob wrote:

I was still a minute slower than Bardet on that descent though...

But he had closed roads

thegreatdivide

NorvernRob wrote:

(including other really crap ones with broken surfaces and loose gravel where I had to brake pretty much constantly)

Col de l'Arpettaz?